| Inorganic rigid particle toughening polymer is one of the promising research fields in material science. In this paper, calcium carbonate (CaCO3) was modified by the method of our group’s patent named solid phase grafting in-situ to get well dispersion of CaCO3in polypropylene (PP) and the reasonable compatibility between CaCO3and PP. The details of modification method can be described as follows. Firstly, CaCO3’s surface was pretreated by maleic anhydride (MAH) or acrylic (AA) to introduce active double bond groups. Secondly, polypropylene wax (PPW) was grafted chemically with MAH or AA to obtain CaCO3-MAH-PPW or CaCO3-AA-PPW particles. The filling effects of modified CaCO3on toughening PP binary and ternary composites were studied in detailIn chapter one, the research was focused on comparing the modification effects of solid phase grafting in-situ and traditional modifying method. MAH, PPW was used to modify the surface of CaCO3to prepare CaC03-MAH-PPW particles by patented method and commercial PP-g-MAH was employed to improve the properties of composites by traditional modifying method. Results show that CaCO3-MAH-PPW particles have high dispersivity in PP and the interfacial interaction between them is appropriate to improve the impact, flexural and processing properties of PP/CaCO3-MAH-PPW composites. However, for the PP/PP-g-MAH/CaCO3composites, the dispersion of CaCO3in PP is poor. But the interfacial interaction between CaCO3and PP is strong because PP-g-MAH can react with CaCO3and entangle with PP chain at the same time. As a result, the tensile strength, heat-resistant performance and crystallization temperature of PP/PP-g-MAH/CaCO3increase.In chapter two, three chemical grafting ratios’CaC03-MAH-PPW were prepared by changing the content of PPW to adjust the interfacial interaction between CaCO3and PP. The effects of chemical grafting ratio of PPW on the properties of composites were researched. The results show that the interfacial interaction between CaCO3-MAH-PPW and PP increases at first and then decreases with the improvement of grafting ratios. And with the enhancement of interfacial interaction, tensile strength and impact strength of composites increase; while the glass-transition temperature (Tg), loss modulus (E") and vicat softening temperature decrease step by step. At the same time the crystallinity of composite increases gradually and crystallization temperature of composite decreases resulting from PPW layer on the surface of CaCO3hindering the heterogeneous nucleation effect of CaCO3.In chapter three, the work is focused on the relationship between properties and phase structure of polymer/elastomer/rigid filler composites. CaCO3-AA-PPW particles were prepared using AA as linkages by the same method. Two processing sequences (one-step and two-step mixing) were used to adjust the phase structure of PP/ethylene-propylene-diene monomer copolymer (EPDM)/CaCO3-AA-PPW ternary composites. One-step mixing is that CaCO3-AA-PPW, EPDM and PP were mixed together in a twin-screw extruder to prepare ternary composites. Two-step mixing are described as follows. Firstly, EPDM was mixed with CaC03-AA-PPW in a twin-roll mill to obtain core-shell structure with CaCO3-AA-PPW as the core and EPDM as the shell. Secondly, the pulverized EPDM/CaCO3-AA-PPW powder was compounding with PP in a twin-screw extruder to prepare ternary composites. The possible phase structures in ternary composites were analyzed from the views of thermodynamics and kinetics. The thermodynamics show that CaCO3-AA-PPW and EPDM more easily separate disperses in PP, but kinetics indicates that two-step mixing can retard somehow the migration of CaCO3-AA-PPW from EPDM resulting in keeping the CaCO3-AA-PPW core/EPDM shell structure in PP matrix, and this structure was supported by SEM. Owing to the core/shell structure, the mechanical properties of PP/EPDM/CaCO3-AA-PPW ternary composites improve, and with the increase of this structure, the toughness of composites is increasing but the melt flow rate decreases. |
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